On Mon, Oct 1, 2012 at 11:00 AM, Arun MURTHY <arun.murthy@xxxxxxxxxxxxxx> wrote: >> On Fri, Sep 28, 2012 at 01:35:01PM +0530, Arun Murthy wrote: >> > +#include <linux/module.h> >> > +#include <linux/slab.h> >> > +#include <linux/err.h> >> > +#include <linux/printk.h> >> > +#include <linux/modem_shm/modem.h> >> > + >> > +static struct class *modem_class; >> >> What's wrong with a bus_type instead? > > Can I know the advantage of using bus_type over class? > >> >> > +static int __modem_is_requested(struct device *dev, void *data) { >> > + struct modem_desc *mdesc = (struct modem_desc *)data; >> > + >> > + if (!mdesc->mclients) { >> > + printk(KERN_ERR "modem_access: modem description is >> NULL\n"); >> > + return 0; >> > + } >> > + return atomic_read(&mdesc->mclients->cnt); >> > +} >> > + >> > +int modem_is_requested(struct modem_desc *mdesc) { >> > + return class_for_each_device(modem_class, NULL, (void *)mdesc, >> > +__modem_is_requested); } >> >> Where is the documentation for your public api functions like this? > > Sure will include this in the next patchset. > >> >> > + >> > +int modem_release(struct modem_desc *mdesc) { >> > + if (!mdesc->release) >> > + return -EFAULT; >> > + >> > + if (modem_is_requested(mdesc)) { >> > + atomic_dec(&mdesc->mclients->cnt); >> > + if (atomic_read(&mdesc->use_cnt) == 1) { >> > + mdesc->release(mdesc); >> > + atomic_dec(&mdesc->use_cnt); >> > + } >> >> Eeek, why aren't you using the built-in reference counting that the struct >> device provided to you, and instead are rolling your own? This happens in >> many places, why? > > My usage of counters over here is for each modem there are many clients. > Each of the clients will have a ref to modem_desc. Each of them use this for > requesting and releasing the modem. One counter for tracking the request > and release for each client which is done by variable 'cnt' in struct clients. > The counter use_cnt is used for tracking the modem request/release irrespective > of the clients and counter cli_cnt is used for restricting the modem_get to > the no of clients defined in no_clients. > > So totally 3 counter one for restricting the usage of modem_get by clients, > second for restricting modem request/release at top level, and 3rd for > restricting modem release/request for per client per modem basis. > > Can you let me know if the same can be achieved by using built-in ref > counting? Is this your model: You have a modem device which can be requested by many clients.This clients can register for a particular service which this modem provides and then after that if it client doesn't need this service then it will call un-register. This can happen for many clients. So what you need is a way to track clients and once no client is in picture, you want to de-allocate all the memory and resource associated with modem device. If this is your model then read on otherwise please skip. What you can do is this: On each modem_register list_add(&modm_dev->entry, &modm_dev_list); and once you de-register, remove the device from the modem_dev_list. Have this in your modem_register function modem->dev->release = modem_dev_release; This will be called once all the device references have been released and you need to remove all the memory/resources associated with your modem device.So you will do the final cleanup modem_cleanup(edev, true); //this will be "false" when the client just does the modem_unregister. Something as below: void modem_dev_unregister(struct modem_dev *edev) { modem_cleanup(edev, false); } static void modem_dev_release(struct device *dev) { struct modem_dev *edev = (struct modem_dev *) dev_get_drvdata(dev); modem_cleanup(edev, true); } static void modem_cleanup(struct modem_dev *edev, bool skip) { mutex_lock(&modem_dev_list_lock); list_del(&modem->entry); mutex_unlock(&modem_dev_list_lock); if (!skip && get_device(modem->dev)) { //do the cleanup here } device_unregister(modem->dev); put_device(modem->dev); } kfree(modem->dev); } > > Thanks and Regards, > Arun R Murthy > ------------------ > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html